Provided is an optical system including, in order from an object side to an image side: a first lens unit having a positive refractive power; a first focus lens unit having a positive refractive power and configured to move toward the object side for focusing from infinity to a closest object distance; and a second focus lens unit having a negative refractive power and configured to move toward the image side during focusing from infinity to the closest object distance, and an interval between each pair of adjacent lens units is changed during focusing. Further, a focal length of the first focus lens unit, a movement amount of the first focus lens unit during focusing from infinity to the closest object distance, a focal length of the optical system, and a total lens length of the optical system are each appropriately set.

Provided is an optical system including, in order from an object side to an image side: a first lens unit having a positive refractive power; a first focus lens unit having a positive refractive power and configured to move toward the object side for focusing from infinity to a closest object distance; and a second focus lens unit having a negative refractive power and configured to move toward the image side during focusing from infinity to the closest object distance, and an interval between each pair of adjacent lens units is changed during focusing. Further, a focal length of the first focus lens unit, a movement amount of the first focus lens unit during focusing from infinity to the closest object distance, a focal length of the optical system, and a total lens length of the optical system are each appropriately set.

The zoom lens, in order from the object side, a positive first lens group that does not move during zooming, a negative second lens group that moves during zooming, a negative third lens group that moves during zooming, at least one lens group that moves during zooming, and a rear group that does not move during zooming. All distances between the lens groups adjacent to each other change during zooming. The zoom lens satisfies predetermined conditional expressions.

The zoom lens, in order from the object side, a positive first lens group that does not move during zooming, a negative second lens group that moves during zooming, a negative third lens group that moves during zooming, at least one lens group that moves during zooming, and a rear group that does not move during zooming. All distances between the lens groups adjacent to each other change during zooming. The zoom lens satisfies predetermined conditional expressions.

A lens 1 has unevenness within an optical effective diameter D of an optical surface 2, an arithmetic mean roughness Ra within the optical effective diameter D of the optical surface 2 is 20 nm or more and 50 nm or less, and an average value of widths W of protrusion portions 3 of the unevenness on an average line C2 of a roughness curve C1 of the optical surface 2 is 1/200 or more and 1/50 or less of the optical effective diameter D of the optical surface 2. The lens 1 is suitably used as a lens that composes a zoom lens or an imaging lens.

A lens 1 has unevenness within an optical effective diameter D of an optical surface 2, an arithmetic mean roughness Ra within the optical effective diameter D of the optical surface 2 is 20 nm or more and 50 nm or less, and an average value of widths W of protrusion portions 3 of the unevenness on an average line C2 of a roughness curve C1 of the optical surface 2 is 1/200 or more and 1/50 or less of the optical effective diameter D of the optical surface 2. The lens 1 is suitably used as a lens that composes a zoom lens or an imaging lens.

There is provided an optical imaging system including a prism, a first fixed lens group, a first movable lens group, a second movable lens group, and a second fixed lens group. The prism is configured to refract light reflected from an object side toward an imaging plane and a reflecting member. The prism is disposed on the first fixed lens group and the first movable lens group is configured to change a position of the imaging plane so that an overall focal length is changed. The second movable lens group is configured to adjust a position of the imaging plane so that a focal length for an object is adjusted. The imaging plane is disposed on the second fixed lens group.

There is provided an optical imaging system including a prism, a first fixed lens group, a first movable lens group, a second movable lens group, and a second fixed lens group. The prism is configured to refract light reflected from an object side toward an imaging plane and a reflecting member. The prism is disposed on the first fixed lens group and the first movable lens group is configured to change a position of the imaging plane so that an overall focal length is changed. The second movable lens group is configured to adjust a position of the imaging plane so that a focal length for an object is adjusted. The imaging plane is disposed on the second fixed lens group.

There is provided an optical imaging system including a prism, a first fixed lens group, a first movable lens group, a second movable lens group, and a second fixed lens group. The prism is configured to refract light reflected from an object side toward an imaging plane and a reflecting member. The prism is disposed on the first fixed lens group and the first movable lens group is configured to change a position of the imaging plane so that an overall focal length is changed. The second movable lens group is configured to adjust a position of the imaging plane so that a focal length for an object is adjusted. The imaging plane is disposed on the second fixed lens group.

An optical lens with an antireflective film includes: a lens substrate; and an antireflective film disposed on the lens substrate. The antireflective film is formed of layers each having a physical thickness of 140 nm or less. In order from an air side, the antireflective film has: a first layer formed as an MgF.sub.2 layer, a second layer, a fourth layer, a sixth layer, an eighth layer, and a tenth layer each having a refractive index of 2.0 or more and 2.3 or less, and a third layer, a fifth layer, a seventh layer, and a ninth layer each formed as an SiO.sub.2 layer.